New microneedle sensor checks fish freshness in under two minutes

Researchers have developed a novel portable sensor that can assess fish freshness in under two minutes by detecting early chemical changes associated with spoilage. Traditional methods of judging fish quality—such as checking appearance and smell—often identify spoilage too late, after visible or sensory signs appear. The new device targets hypoxanthine (HX), a molecular marker that rises quickly as fish decomposes post-mortem. Unlike current HX testing methods that require lab equipment and skilled technicians, this sensor uses a four-by-four microneedle array coated with gold nanoparticles and an enzyme that reacts specifically with HX, enabling rapid, on-site freshness evaluation. The microneedles penetrate just below the fish’s surface to detect chemical activity where spoilage begins. When pressed against the fish, the enzyme reacts with HX, causing electrical signal changes that the sensor interprets to determine freshness. Tested on salmon samples left at room temperature for up to 48 hours, the device detected HX levels as low as 500 parts per billion